140 J. F. Fitzpatrick, Jr. 



during Miocene times and expanded and diversified as the more south- 

 ern lands emerged from the sea and new drainages developed. 



Procambarus , the largest of the crawfish genera, is expectedly the 

 most complex. And no significiant argument can be made against the 

 supposition that among its members are the species most like the ances- 

 tral Cambarinae. Equally, those species are certain members of P. (Pen- 

 nides) and of the Pictus Group of Ortmannicus. Here an interesting 

 geographic dichotomy occurs. The Pictus Group is unquestionably 

 associated with the Atlantic Coastal Plain, whereas Pennides is found in 

 the Atlantic drainage and the Gulf drainages as far west as Texas (plus 

 an isolate in northern Mexico). The two "groups" within Pennides have 

 been noted, as have been the geographic relationships (Fig. 1, 2). 



I suggest a very early isolation of the ancestral procambarid stock 

 into eastern and western populations, possibly in the vicinity of 

 northeastern Alabama or northwestern Georgia. Not long afterward, 

 possibly by the large Midway river of Grim, the proto-Pennides were 

 divided. Fitzpatrick and Hobbs III (1968) noted the absence of members 

 of the subgenus from the alluvial plain of the Mississippi River and 

 suggested that such a feature, which denies proper environmental situa- 

 tions, is as effective a barrier as if a dry-land bridge were interposed. 

 Perhaps such a barrier acted to isolate a primitive stock of Pennides. 

 During Miocene times the western stock retained the cephalic process 

 but diversified into a complex of species. Significantly, most widespread 

 members are west of the Mississippi River, but P. (Pe.) vioscai and P. 

 (Pe.) ouachitae have variants on the east side. Recently, Hobbs, Jr., and 

 I have discovered what appears to be a population of P. {Pe.) elegans 

 Hobbs on the east side, but that species seems to be of limited distribu- 

 tion on both sides of the river. Procambarus (Pe. ) ablusus Penn is essen- 

 tially isolated in western Tennessee. The siblings, P. (Pe.) clemmeri and 

 P. (Pe.) penni, are found south of the "river" of Brown (1967), indicat- 

 ing their divergence and spread occurred no earlier than the Pliocene. 

 The other Mississippi species, P. (Pe. ) lagniappe Black and P. (Pe. ) lylei 

 Fitzpatrick and Hobbs, seem to be very restricted, regional isolates. 



Farther eastward are the species of Pennides that lack a cephalic 

 process. For these, Hobbs's (1981:36-38, 53-54) arguments seem valid. 

 The two enigmas to me are P. (Pe.) petersi Hobbs and P. (Pe.) versutus 

 (Hagen), both of which have a cephalic process. Otherwise, P. (Pe.) 

 petersi is close to P. (Pe.) raneyi Hobbs, morphologically and geo- 

 graphically. Perhaps this is indicative that the eastern proto-Pennides 

 retained for a short while the cephalic process, but most populations 

 lost it early. Surely the most difficult to interpret is P. (Pe.) versutus. 

 Hobbs (1981:38) said, "Considering the Georgia representatives of Pen- 

 nides alone, clearly the most disjunct of the five is Procambarus versu- 

 tus . ..." I concur, but add that it is different from all other Pennides, 

 too. It shares many characteristics with the highly restricted P. (Pe.) 

 lylei. Both have a distinct shoulder on the cephalic surface of the male 



